Portable metal knife sharpener



FIG. 1 is a perspective view of a portable metal knife sharpener showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines shown in the drawings depict portions of the portable metal knife sharpener in which the design is embodied that form no part of the claimed design. 

CLAIM The ornamental design for a portable metal knife sharpener, as shown and described. 